AN EQCM ANALYSIS OF PASSIVATION PROCESS OF COPPER THIN FILM

摘要

The passivation processes of copper thin films in deaerated borate soultions of pH 6.5 - 8.4 were analyzed by an electrochemical quartz crystal microbalance (EQCM). The simultaneous measurement of changes in mass and current has succeeded in separating the anodic current flowed during passivation into two partial currents of passive film growth, i_o2-, and metal dissolution through the film, i_(Cu)2+. It was found that the linear relation between log i_o2- and log i_(Cu)2+ held, from which the ratios of the transfer coefficients, α_o2- / α_(Cu)2+ ,were obtained. The average value of α_o2- / α_(Cu)2+, thus obtained was nearly unity, independent of potential and solution pH. Moreover, EQCM could monitor the breakdown process of the passive film due to an addition of SO_4~(2-) to pH 8.4 borate solution.